Estradiol-17β stimulates aromatase activity and reversible sex change in protandrous black porgy,Acanthopagrus schlegeli

Abstract

The objective was to investigate the effects of estradiol-17β (E2) on gonadal development, spermiation, gonadal aromatase activity, and the concentrations of plasma sex steroids and vitellogenin in 2-year-old protandrous black porgy, Acanthopagrus schlegeli. Black porgy were divided into two groups, one fed a control diet and the other a diet mixed with E2 (4.0 mg/kg feed) for 4½ months. Significantly lower GSI was observed in the E2 group. Fish treated with E2 showed completely suppressed spermiation, and 38% had developing vitellogenic oocytes in the gonad (an evidence of sex reversal in 2-year-old fish). Higher gonadal aromatase activity and plasma E2 concentrations and lower concentrations of plasma 11-ketotestosterone (11-KT) were observed in the E2 group. After finishing 4½ months of E2 treatment in the early spawning season, the gonadosomatic index increased and spermiation resumed in the E2 group (which was fed a control diet) during the mid- or late-spawning season. Steadily increasing levels of plasma T and 11-KT and decreasing gonadal aromatase activity and plasma vitellogenin concentrations were observed in the E2 group. The present data show that E2 induced a temporary and reversible sex change (only a small proportion of the fish). Elevated aromatase activity in gonads, elevated E2 levels in plasma, and diminished levels of plasma 11-KT are associated with the occurrence of sex reversal in protandrous black porgy. J. Exp. Zool. 280:165–173, 1998. © 1998 Wiley-Liss, Inc.